A communication system is a facility that enables communication between two or more entities such as user terminal equipment and/or network entities and other nodes associated with a communication system. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on.
The communication may be provided by fixed line and/or wireless communication interfaces. A feature of wireless communication systems is that they provide mobility for the users thereof. An example of a communication system providing wireless communication is a public land mobile network (PLMN). An example of the fixed line system is a public switched telephone network (PSTN).
A cellular telecommunication system is a communications system that is based on the use of radio access entities and/or wireless service areas. The access entities are typically referred to as cells. Examples of cellular telecommunication standards includes standards such as GSM (Global System for Mobile communications), GPRS (General Packet Radio Servers), AMPS (American Mobile Phone System), DAMPS (Digital AMPS), WCDMA (Wideband Code Division Multiple Access), UMTS (Universal Mobile Telecommunication System) and CDMA 2000 (Code Division Multiple Access 2000).
A communication system typically operates in accordance with a given standard or specification which sets out what the various elements of a system are permitted to do and how that should be achieved. For example, the standard of specification may define if the user, or more precisely user equipment is provided with a circuit switched service or a packet switched service or both. Communication protocols and/or parameters which should be used for the connection are also typically defined. For example, the manner in which communication shall be implemented between the user equipment and the elements of the communication network is typically based in a predefined communication protocol. In other words, a specific set of “rules” on which the communication can be based needs to be defined to enable the user equipment to communicate via the communication system.
At the time of writing of this patent application, enhancements of the uplink DCH (Enhanced DCH, EDCH) are being standardized for packet data traffic for release 6 of the 3GPP standards. Some of the associated 3GPP standards are at least (but not limited to) the following: 3GPP TR 25.896, 3GPP TR 25.808, and 3GPP TS 25.309.
Enhancements are reached according to currently discussed standard versions by distributing some of the packet scheduler functionality to the Node B network nodes in order to have faster scheduling of bursty non real-time traffic than the layer 3 mechanisms in RNC facilitate. The idea is that with faster link adaptation it is possible to more efficiently share the uplink power resources between packet data users: when packets have been transmitted from one user the scheduled resource can be made available immediately to another user. This avoids the peaked variability of noise rise, when high data rates are being allocated to users running bursty high data-rate applications.
In the currently specified architecture, the packet scheduler is located in the RNC and therefore is limited in its ability to adapt to the instantaneous traffic, because of bandwidth and delay constraints on the RRC signalling interface between the RNC and the UE. Hence, to accommodate the variability, the packet scheduler must be conservative in allocating uplink power to take into account the influence from inactive users in the following scheduling period—a solution which turns out to be spectrally inefficient for high allocated data rates and long release timer values.
In current specifications for EDCH, much of the packet scheduler functionality is transferred to the Node B, i.e. there is a Node B scheduler that takes care of allocating uplink resources. For transmission of data, the UE selects a E-TFC that suits the amount of data to be transmitted in its RLC buffer, subject to constraints on the maximum transmission power of the UE and the maximum allowed power. If needed, UE can request for higher bit rate by sending Rate Request messages (RR) in the uplink, and the Node B decides whether to grant or not additional resources by answering with rate grant messages in the downlink. The grant messages are of two kinds: Relative Grants (RG) and Absolute Grant (AG). Relative grants are relative to the actual used resource by the UE. The absolute grant allocates resources to the UE in an absolute manner in terms of power. When to use AG or RG to adjust the resources allocated to the UE is fully subject to the decision done in the network. The AG and RG messages are transmitted in the downlink using specific physical channels designed for this purpose, namely E-AGCH and E-RGCH.
Also the current EDCH specifications bring a similar L1/MAC layer HARQ retransmission mechanism between UE and Node B in the uplink as in HSDPA for the downlink. The fast HARQ is be based on N-process SAW (Stop-And-Wait) HARQ, where HARQ combining is performed at Node B L1 (layer 1). For the 2 ms TTI (transmission time interval), 8 SAW HARQ processes are defined in the current standard versions, and for the 10 ms TTI 4 processes are defined in the current standard versions.
According to certain current proposals, each HARQ process is to be scheduled independently for the 2 ms TTI. There is a fixed timing relationship between the DL (downlink) and the UL (uplink) which tells to which HARQ process the received AG or RG command (AG/RG) applies as shown in FIG. 1. For each AG or RG command received, the UE knows exactly to which HARQ process it applies due to the known timing relationship.
These proposals have certain problems. For example, scheduling each HARQ process independently requires a lot of signalling and can be considered more susceptible to signalling errors.
It has been proposed to have an 8 bit process allocation string defined at Layer 3: each bit tells whether the UE is allowed to transmit in uplink for that particular HARQ process or not. This known proposal would enable considering the scheduling commands applicable to all active HARQ retransmission processes and thus reduce required amount of signalling and susceptibility to signalling errors and still have the means for the network to control which HARQ retransmission processes are allowed to transmit. However, layer 3 signalling is too slow to allow a fast activation. Besides the Node B scheduler is located at Layer 2 in the Node B. Interaction with Layer 3 at RNC for scheduling issues is not optimal.